The invention relates to yarn suitable for tufting, especially to form carpet face fiber, and other applications. The yarn comprises a blend of fibers including a first, preferably synthetic, base fiber, ring spun or wrap spun with a second fiber that at least partially comprises a heat-activated adhesive material having a melting point substantially below that of the base fiber. In a process for production of a yarn suitable for tufting, particularly for use in a carpet, exposure of the yarn to usual process conditions for twist setting the yarn causes the heat-activated adhesive material in the inserting or wrapping fiber, as appropriate, to melt substantially completely and flow to points of intersecting base fiber filaments to create a bond upon subsequent cooling, thus altering properties and performance of the resulting product.
It has been known to blend non-adhesive fibers with potentially adhesive fibers to form a yarn or other textile structure or article, then to activate the potentially adhesive fibers to bond them to contacting fibers, thus modifying end-use properties of the yarn. U.S. Pat. No. 2,252,999 to Wallach, issued Aug. 19, 1941, provides a process wherein a yarn comprising an admixture of non-adhesive and potentially adhesive fibers is formed, the potentially adhesive fiber is activated, and the fibers compacted while in an adhesive condition so that they adhere to each other at points of contact U.S. Pat. No. 3,877,214 to Van der Werf, issued Apr. 15, 1975, discloses a twist-free yarn comprising a polyamide fiber melting under a relatively low temperature as a bonding component. U.S. Pat. No. 3,494,819 to McAlister, issued Feb. 10, 1970, discloses a blend of fusible and non-fusible polyethylene terephthalate fibers incorporated into fabric, wherein the finished fabric is heated to fusion temperatures to provide improved pill resistance U.S. Pat. No. 3,978,267 to Selwood, issued Aug. 31, 1976, discloses a substantially twistless compact yarn comprising a proportion of potentially adhesive fiber which has been activated to bond contacting fibers.
Cut-pile carpet is customarily produced from staple yarns or bulked continuous filaments yarns. For example, staple fiber is conventionally carded, pinned, and spun or wrap spun into a singles yarn, which typically is twisted and plied with similar yarn to form a 2-ply or 3-ply yarn construction. This yarn is twist set by utilizing one of several commercially available twist setting processes such as the Suessen or Superba processes.
In a typical process the yarn is passed through a heated chamber, while in a relaxed condition. The temperature of this process step is crucial to the proper twist setting of the base fiber, to obtain desired properties of the final carpet product. For nylon-6 base fiber, the conditions for this step are typically 190-200xc2x0 C. with a residence time of about 60 seconds for the Suessen process and about 125-140xc2x0 C. with a residence time of about 60 seconds for the Superba process. The Superba process utilizes saturated steam and thus the yarn is subjected to a much higher level of humidity than in the Suessen process.
Similarly, bulked continuous filament yarn is produced according to various conventional methods. Twisting, entangling, or direct cabling may be utilized in various processes. For example, a 2-ply twisted yarn combining 2 ends of 1185 denier 70 filament nylon-6 yarn is prepared and subjected to conventional twist setting conditions, such as that for the staple yarn above, or in an autoclave at 132xc2x0 C. in saturated steam with a residence time of about 40 to 60 minutes.
It is known to wrap fiber, both staple and continuous filament, with a binder strand to physically bind the wrapped fiber to permit downstream processing. See, e.g., U.S. Pat. No. 4,495,758 to Stahlecker et al. and U.S. Pat. No. 4,668,553 to Scott et al. Neither of these patents, however, uses or suggests the use of a binder strand or fiber that contains heat-activated adhesive material.
Multiple ends of the twist set yarns are tufted into cut pile carpet and conventionally finished to obtain the desired carpet product.
Yarn, preferably synthetic, comprises at least one bundle of fiber, the fiber being ring spun or wrap spun with a second fiber (either an insert fiber in the case of ring spun or a wrapping fiber in the case of wrap spun) comprising a heat-activated binder material, preferably a fiber, having a melting point range of about 105 to 190xc2x0 C., preferably 165 to 190xc2x0 C., under ambient humidity conditions, such that the yarn comprises a total of 0.1 to 12, preferably 0.25 to 10, more preferably 0.5 to 8, weight percent binder material. The preferred fiber bundle comprise staple fibers, preferably in the form of a silver. Alternatively the bundle of fibers may be continuous filaments. The preferred second, binder fiber is a copolyamide, more preferably a copolyamide of the nylon 6/nylon 6,6 type. The preferred bundle of fiber is nylon 6. The present invention is also an article, preferably tufted, more preferably a carpet, made from this yarn. The present invention is also a process of producing a yarn suitable for tufting; the process comprising the steps of:
a. forming a bundle of fiber, preferably by spinning staple fiber;
b. ring spinning or wrap spinning the bundle of fiber with a second fiber comprising a heat-activated binder material having a melting point range of about 105 to 190xc2x0 C., preferably 165 to 190xc2x0 C., under ambient humidity conditions to form a yarn comprising 0.1 to 12, preferably 0.25 to 10, more preferably 0.5 to 8, weight percent of the binder material;
c. heating the yarn sufficiently to melt the binder material; followed by
d. cooling the yarn, preferably during twist setting, to solidify the binder material.
With ring spinning, the insert fiber is inserted before the front delivery roll into a continuous bundle of base fibers, preferably staple fibers in a silver. This invention also relates to yarn made in accordance with the aforesaid process.
When the yarn is twisted, plied and twist set by conventional processes, for example 190-200xc2x0 C. Suessen twistsetting with a residence time of about 60 seconds, and the treated yarn tufted into cut-pile carpet, the resulting carpet displays enhanced carpet tuft appearance, improved resilience, and reduced change of appearance with use.
Applicant has discovered that by incorporation of a minor proportion of heat-activated binder fiber having substantially lower melting point than the base fiber into the yarn construction, the standard heat conditions for twist setting the yarn will cause the binder fiber to melt, substantially losing its identify as a fiber. It will flow to intersecting points of the base fiber and upon subsequent cooling will encapsulate and bind fibers and yarn together, thereby retaining the twist in cut-pile carpets. Carpets made with the yarn of this invention can be improved in surface, aesthetics, hand, durability and wear performance. By careful selection of the binder fiber desired improvement is xe2x80x9cbuilt-inxe2x80x9d to the yarn, with no additional process steps required by the yarn spinner, the carpet manufacturer, or in dyeing and finishing.
The base fiber is selected from known synthetic fibers suitable for carpet use; such as, polyamides, nylon-6 and nylon-6,6, polyesters, and polyolefins, as well as material fibers, such as cotton and wool.
The binder fiber is selected to provide good adhesion to the base fiber. It is important that the melting point of the binder fiber be in the range of 105-190xc2x0 C., preferably 165-190xc2x0 C., under ambient humidity conditions. This range ensures that the binder fiber will melt during the conventional twist setting process yet will provide adequate adhesive properties during any subsequent dyeing steps and final use. A saturated steam environment, such as in an autoclave, reduces the fiber melting point of polyamide binder fibers dramatically.
A preferred class of binder fiber for use with polyamide base fibers are copolyamides within the specified melting point ranges. Suitable copolyamides of the 6/66/12 type and a process for their production are disclosed in U.K. Patent 1,168,404, issued Oct. 22, 1969 to Inventa A. G., incorporated herein by reference. A melt bonding copolyamide adhesive fiber is commercially available from EMS as GRILON(copyright) type K 140 (melting range 130-140xc2x0 C.) and type K 115 (melting range 110-117xc2x0 C.) copolyamides of the 6/66 Type as in U.S. Pat. No. 5,478,624 to Lofquist.
The binder fiber can be blended, wrapped around, or inserted into base fibers, and the resulting fiber blend can then be processed in known ways. It is important to ensure a thorough blending when the binder fiber is blended with base staple fiber to avoid potential clumps in the finished carpet. The fiber blend should contain 0.1-12 weight percent binder fiber, preferably 0.25 to 10 weight percent, and more preferably 5 to 8 weight percent. Higher amounts cause undesirable harshness of hand due to the conditions of the twist setting process causing the binder fiber to melt substantially completely. Ring spun or wrap spun yarns prepared from such a fiber blend and subjected to thermal activation can provide strength properties approaching that of bulked continuous filament (BCF) yarns. Properties of BCF yarns can also be enhanced.
By selection of the thermally activated binder fiber within the weight percent ranges and melting point ranges specified it is possible to modify end-use properties of the finished carpet to improve wear resistance, resilience, reduced change of appearance over time and with use, and to increase hand, lustre and apparent value. Denier per filament, cut length, fiber cross-section, crimp type and frequency, surface finish, melt viscosity, softening point, melting point, dye affinity, and other properties are crucial to achieving ideal properties in the final product. A proper selection of the binder fiber must be made to obtain the desired, or optimum results from the finished carpet product. This will depend on numerous factors including the denier, length, crimp, finish, and other properties of the base fiber product.
With the utilization of this invention, twist setting conditions normally used are sufficient to activate the binder fiber, to create bind points which strengthen the final product, thereby imparting other characteristics which are desirable. For the Suessen process, under relatively low humidity conditions, the twisted yarn is subjected to a temperature of 190-205xc2x0 C. for a residence time of 50-60 seconds. In the Suessen process motion of the fiber while in the relaxed state, caused by vibration or air currents, sufficiently motivates the molten binder fiber to flow to the intersecting xe2x80x9ctouch pointsxe2x80x9d of the base fiber, as a function of the melt flow properties of the binder fiber and surface characteristics. As the fiber emerges from the elevated temperature condition, the binder solidifies and encapsulates or bonds two or more base fibers together at intersecting points in a durable bond. Subsequent processing including dyeing, finishing, and backcoating using commercial processing methods does not soften the bond points sufficiently to weaken them, but rather will strengthen them. The resultant carpet can be of many forms, but a typical style would be cut-pile carpet with about 40 ounces per square yard of face yarn including the binder, with an attached backing. Carpet construction would be typically {fraction (5/32)}xe2x80x3 gauge, xc2xexe2x80x3 pile height, and the carpet would be dyes, dryed, backcoated, and sheared using normal processing techniques. The yarn of the invention would also provide important property improvements in the production of loop-pile carpet.